The present invention relates to a device for removing heat from a neutron-producing plasma. Heat energy is transferred from the plasma by means of neutron radiation and absorbed within a circulating solid media that is cooled for extracting heat energy for use.
The neutron radiation is produced in a plasma containing ions of such as deuterium and tritium that react to produce helium and energetic neutrons. The plasma containing such reactions is fully described in U.S. Pat. No. 3,037,921 to Tuck, entitled "Method and Apparatus for Producing Neutrons and Other Radiations". This patent is expressly incorporated herein for the purpose of describing such a neutron-producing plasma.
A neutron-producing plasma of this type can be produced not only by the reaction of tritium and deuterium to form helium ions and neutrons but also by various other reactions. For example, the reaction of deuterium with deuterium, helium isotopes with deuterium and helium with protons are contemplated. Reactions of these types also are suggested in the above patent as a source of neutron radiation.
These neutron-producing reactions occur at extremely high temperatures and release very large quantities of energy. Previous coolant systems thus have been severely tested in regard to strength of materials and heat transfer rates due to the high temperatures and energetic output of these reactions. In addition, the problem of breeding additional fuel, particularly tritium, often is approached by combining this breeding function with that of heat transfer.
One proposed system employs the gravity flow of solid lithium oxide microspheres for removing heat from the neutron-producing plasma as well as for breeding tritium through a neutron-lithium reaction. As is well known, both Li.sup.6 and Li.sup.7 react with neutrons to produce tritium and helium. However, the Li.sup.7 isotope has a greater propensity for reaction with energetic neutrons, which reaction additionally produces a secondary slow neutron. Other similar systems have proposed the use of molten lithium metal for this combined heat transfer and breeding function.
The combination of heat removal and tritium breeding in a single media, although appealing from a functional and utilitarian viewpoint, has inherent and serious disadvantages. A major difficulty is that the heat transfer media becomes radioactive with the production of tritium which necessitates complicated and cumbersome maintenance techniques along with extended waiting periods for the decay of radioisotopes. The problem of tritium diffusion from the heat transfer system likewise must be considered. In addition, optimum breeding materials and conditions do not necessarily provide optimum characteristics for heat transfer such that a compromise as to desiderata in each of these functions may be required. Where lithium metal is selected its extremely high chemical reactivity and corrosiveness requires that it be kept scrupulously free of materials such as oxygen and nitrogen with which it reacts.